Fluid metering device



July 2, 1963 Filed March 22, 1960 D. H. LAING ETAL FLUID METERING DEVICE 2 Sheets-Sheet 1 PATENT AGENT July 2, 1963 D. H. LAING ETAL 3,095,892

FLUID METERING DEVICE Filed MaIGh 22, 1960 2 Sheets-Sheet 2 /N VEN TGRS DA V/D H. LA /N6` PA Tl/7' A GEA/7 ite States This invention relates to an apparatus for metering one iluid into another and to an apparatus for providing a lluid passage; the invention is particularly adapted for the metering of iluoride solution into a water supply.

By tluids we include compressible fluids such as gases and incompressible fluids such as liquids.

By compressible container we mean any lluid container whose volume may be decreased by external pressure on one or more walls of the container and thus we include for example, such containers as flexible plastic bags, piston cylinders or otherwise rigid containers having a diaphragm as one wall.

We use the term sinuous to include the meanings helical, windingj crooked, bending in and out, and of a serpentine or undulating form.

It is an object of this invention to provide means for metering a lirst fluid into a second fluid, when the latter is flowing, which uses a pressure differential from a higher to a lower pressure in the second fluid, as the motivating force to move the lirst iluid into the second.

-It is an object of this invention to provide such means wherein the proportion of the first lluid metered into the second is controlled to desirable amounts within a range of higher pressures in the second fluid when it is flowing and means are provided which are designed to keep the higher pressures below the upper limit of said range.

It is an object of this invention to provide means for metering a first iluid into a second fluid when the latter is flowing by using a pressure differential from a higher to a lower pressure in the second iluid, as the motivating force to move the rst fluid into the second and wherein the proportion of the lirst lluid metered into the second is controlled to desirable amounts within a range of higher pressures and having means to prevent the tlow of rst iluid into the second when the higher pressure falls below the lower limit of said range.

It is an object of this invention to provide means for metering a first fluid into a second when the latter is flowing, by using a pressure ditierential from a higher to a lower pressure in the second fluid as the motivating force to move the lirst lluid i-nto the second wherein the proportion of first iluid metered into the second tluid is constant over a wide range of iluid flow rates.

The invention provides a device for metering one tluid into another, which latter is tlowing in a flow path, the iluid being metered being contained in a compressible container, the other fluid being provided with a fluid llow path across a llow restrictor causing a drop from a higher to a lower pressure, means for applying said higher pressure to compress said container and a restrictive path or passage from said container to the low pressure portion of said flow path whereby llow in said main line causes the metering of some of the container tluid into the main line while a cessation of flow in the main line removes the pressure differential and stops the tluid llow from the container. The invention provides designs for the flow path restrictor and the restrictive path or passage which allow llow respectively therethrough proportional to the applied pressure across them. It will be seen that the device may thus be designed to be linear, that is, to meter proportionally, from zero to maximum flow in the lluid flow path. On the other hand, it may be that such proportional metering may only be possible below a predeatent O Tice termined value of higher pressure in which case there may be provided on the upstream side of said ow restrictor a second restrictor for the said flow path to tend to maintain the higher pressure within the upper limit ott said range. The ellectiveness of the second restrictor will of course depend upon the range of source pressures for the iluid tlowing in the ow path. Where the flow path tluid is water from a city water supply, the upstream restrictor will be selected to keep such higher pressures below the desired upper limit of higher pressures after considering the range of pressures to be encountered in the city supply lines.

It may be desirable, for economy of design, to provide substantially proportional metering only above a predetermined lower value of higher pressure in which case means are provided to pre-vent any flow of iluid from the container below such predetermined lower value.

As will be seen from the specific embodiment to folf low, there are also disclosed safety arrangements whereby under conditions of no flow or reverse llow in the llow path no seepage or diffusion from the container to the llow path can take place, and no llow from the llow path to the container can take place in the event of back pressure in the flow path. The importance of these safety precautions will be obvious in the event that the nature of the container Iluid was such that danger might accrue from greater .concentrations iof the container fluid in the main line than desired.

`Our invention us-es a tluid flow restrictor designed so that an increase in llow path fluid pressure upstream from the restrictor causes la consequential increase in rate of llow of the ilu-id. Such a principle permits the design of a device which will provide a flow proportional to pressure even with an incompressible fluid.

There is further disclosed a device for providing a restricted lluid path or passage formed by a pair of bodies having respective walls in immediate contact, providing at least one sinuous groove in the surfaces of one or other of the respective ybodies extending along the contacting surface of said wall or in lthe contacting surfaces of both walls whereby a path for fluid may -be defined from a fluid source connected to said at least lone `groove and a path for tluid may be defined from said lat least one groove connected to a lluid outlet, such connections being at spaced locations.

It has been found that this method of design for a restricted iluid passage has several advantages, and in particular the following:

(l) Due to the greater length of fluid passage which may be thus convenien-tly provided, the required resistance to fluid ilo-w may be `achieved with a passage of relatively large cross section. The size of passage which may be used reduces the chance of clogging yby iinepsolids and thus the liquid `to go through the passage may carry such line solids in coarser form than otherwise. This is an advantage over prior restrictive devices which comprise a porous body presenting a relatively short effective passage length rand having a multitude of small passages therethrough.

VOur invention allows a great length of passage t-o be contained in a body of very compact form yand dimensions whereby the passage may be larger than the mean passage diameter of the aforesaid porous body. Thus, clogging is much less likely with our invention but the llow resistance may be made `as great as with the aforesaid porous bodies.

(2) It has been found that with proper -design the rate of flow to pressure relationship maybe kept linear. A constant ratio Vbetween pressure `drop across the device and fluid llow therethrough may be achieved when the groove cross section and length are such as to cause laminar flow within the range of pressures applied.

(3) The construction described has been found to lend itself readily to plastic molding techniques.

(4) The sinuous passage construction allows the design of a restrict-ive passage of considerable length to be provided in a member of much shorter length.

Preferably, the device is constructed of a body having at least one surface defining a large central bore therein wd a body having a surface adapted to make a sliding 't in the bore, and to -rest against the defining surface. The groove is preferably made in helical form and is made in oneof the surfaces so that when the second member is placed inside the first, a passage is dened therebetween.

This design permits examination or easy cleaning of the interior surfaces of the grooves so formed by removal of the second body to lay bare the tirst body bore.

The device just described -is particularly adapted for metering quantities of one fluid of one order into quan-l tities of fluid of a much higher order.

It will be seen that the device would be of value for individual fluoridation of the water supply to a dwelling house or to an individual water outlet or the like and it is this construction that is described in the specific embodiment. Y

Fluonidation requires the introduction of very small quantities of fluoride solution into a water supply in Yproportions which must be carefully controlled due to the harmful effects of over-concentration of such fluoride in the water supply. The device to be described is particularly adapted to control the supply of such fluoride solution.

FIGURE l is a vertical cross-section through the device;

FIGURE 2 lis an enlarged view of a part of FIGURE l;

FIGURE 3 is an enlarged View of a part of FIGURE 1 showing an element of the apparatus in a different position to that shown in FIGURE 2;

FIGURE 4 is an enlarged view of another FIGURE 1;

FIGURE 5 is a reduced perspective view of the outside of the device; and

FIGURE 6 shows a slight modification of the device in FIGURE l.

In the drawing is shown the fluid metering device comprising a body l@ having a central bore 12 therein. At each end of bore 12 the dening walls thereof are threaded for attachment to a water line and the bore therefore delines a flow direction and an upstream` end i4 and a downstream end 16. The bore 12 is sometimes referred to as a tiow path or a main flow pat and the fluid flowing therein is sometimes refer-red to `as lthe second fluid. It will be understood that a suitable screen may be placed in the main iiow path on the upstream side of body to prevent large objects approaching the body.

Toward the upstream end 14 of the bore is provi-ded a tiow restrictor 18 adapted to foi-rn a resistance to iiow in the bore 12 hereinafter also referred to as the main iiow path. The restrictor l causes Va material pressure drop P1-P2 between the pressure P1 on the upstream side of .the restrictor and the pressure P2, on the downstream side; The pressure P1 is referred to herein as :the higher pressure and the pressure P2 as ythe lower pressure.

The how restrictor I8 illustrated in FIGURE 4, is designed to allow quantity of liow per unit time to tiow therethrough 'at a rate proportional to the pressure differential across the re'strictor. The rest-rictor may be of any desired design Ito allow such proportional flow ibut in its preferred lform is an annular disc of flexible stretchable resilient material, such as rubber having a central laperture I9. The restrictor 1S is preferably anchored against longitudinal movement along bore 12 in the .downstream 'direction by any desired means such as by a shoulder res-.ting in a groove in bore 12. The restriotor ISis designed so that lthe pressure of fluid flowing in bore 12 iiexes the material of the disc about aperture 19, downstream relative -to the lperiphery and is designed so that such tlexure part of widens aperture 19 so that with proper design the rate of ow of fluid in quantity per unit time (hereinafter referred to as the iiow rate) through aperture 19 will be proportional to the pressure differential across the restrictor 1S. In the preferred embodiment such design is accomplished by ensuring that the upstream face of the disc, adjacent the aperture 12 slopes in a downstream direction toward the aperture to meet the downstream face of the disc at the edge thereof defining aperture I9. The slope of the upstream face is such that downstream ilexure of the inner edge thereof @FIGURE 4) will expand the effective aperture 1 9 in progressive degrees varying with the Vpressure differential across the disc. The operation of the restrictor 18 is that pressure P1 on the upstream side thereof, iiexes the inner extent of restrictor 18 in the downstream direction tending to increase the size of aperture 19 in accord with the higher pressure Pl. I-n this way the characteristics of restrict-or 18 may be so ydesigned Ithat the ilow through the aperture is vproportional to the pressure differential Pl-PZ. The design will in sorne cases be assisted by the fact that the upstream side of restrictor 1S is curved inwardly in the direction of tiuid flow.

Below Athe main bore 12 is provided a uid tight housing`20, preferably of cylindrical form. In the housing is contained a flexible fiu-idtight container or `bag 22. Fluid in bag 22 is sometimes referred to as the second fluid. The bag 22 is detachabiy suspended by any desired vmeans from -a holder 24 which formslthe top of the bag 22. The holder is provided with an internally threaded sleeve 27 for attaching the holder to a boss 26 projecting downward-ly from the body it), and the dimensions of holder 24 and bag 22 are `such that there is a space 28 between the housing and the side and bottom walls of the bag 22. Means are provided for evacuating air from the space 2S through housing 2th such as bleed screw 21.

In a preferred form of the invention body' 10 is a thick disc, circular in plan view (please refer to FIGURE 5 as well as FIG-URE l) with bore 12 extending diametrically thereacross. As shown, the housing 2t? may be threaded onto the body 10. When used as a fluoridator for a dwelling house, it is impor-tant that the housing be readily detachable for easy replacement of fthe 'bag 22. However it is sometimes felt that threaded joints are not desirable because of the risk 0f damage to the thread. If this is so the housing may conveniently -be attached fto the body by iianges and bolts or by any other easily detachable means.

A bore 30 connects bore 12 on the upstream side of the restrictor 18 with the space 28 the junction between the housingV 2t) .and -body Iii making the space 28 otherwise iiuid tight. The housing 20 and body 16 maybe threaded together as shown, with a suitable sealing washer therebetween.

Means are provided for connecting the inside of bag 22 with 'bore I2 on the downstream side of the restrictor 18 which will now be described.

The boss 26 is provided with a central bore 34 extending from the bottom thereof to the bore 12 on :the downstream side of restrictor 18. 'Bore 34 is of wide diameter in its lower portion but tapers toward bore 12 `at 35 and preferably the dening surface thereof is a surface of revolution. Adapted to slide upwardly into the bore 34 is plug 36 having a surface complementary to and adapted to `be placed in juxtaposition with the defining surface of bore 34. Plug 36 has shoulder lianges 3S adapted to bear on the lower surface of the boss 26. In such position complementary upper tapering walls 37 of the plug abut the 'tapering walls of the bore 34 but extend upwardly for a short distance into the bore 12.

The tapering portion of plug 36 is provided with a bore 39 opening into the bore 12 and the bore 39 is connected at its lower end to a cylindrical chamber 40 defined by top wall 41 and side walls 42. The Walls 42 are provided with one or more helical grooves 44 extending like threading from the Vbottom to top of side walls 42. The grooves 44 are of predetermined cross section for a purpose to be hereinafter described. Adapted to t in the chamber defined by walls 41 and 42 is a block 46. The block 46 is shaped to abut rwith a tight tit the walls 42 and is provided with studs 4S on the upper surface thereof adapted to contact top walls 41 and provide a space between the upper surface of the block and the top wall of the chamber to allow llow between grooves 44 and bore 39. The abutment between the rsurfaces of block 46 and the surfaces of walls 42 must be immediate, that is the lit must be such that there can be no leakage between them out of grooves 44.

The outer surface of the boss-26 is threaded and the sleeve 27 is screwed `over the top thereof. The holder 24 on the upper surface inside sleeve 27 is provided with a central stud 52 adapted to contact the bottom wall of the block 46 and hold it so that studs 48 contact the upper wall of the chamber 40. An annular washer 54 is seated on the upper surface of holder 24 and seats the lower surface of the tapered plug to hold the latter in place in the bore 34. Ports 56 extend through the holder 24 inside sleeve 27 at a portion of the upper surface thereof uncovered -by the washer 54.

A membrane 58 extends conically from the washer 54 to the stud S2 and is tensioned lightly Adownwardly against .the stud. The membrane 58 is so tensioned as to be easily moved upwardly by a greater pressure below the membrane than above but to seal off the bag 22 against upward diffusion of the materials therein when no pressure differential exists. It will be noted that membrane 58 is also adapted to prevent flow into the container 22 in the event of back pressure and hence acts as a one Way valve. The membrane 5S and washer 54 are preferably of plastic and are contiguous land formed in a single moulding operation.

The proportional restrictor 18 and the restricted fluid passage or path composed of the grooves 44 may be treated as parallel resistances to liuid flow, both acted upon by the pressure differential P1-P2 and with proper design causing an amount of fluid from container 22 to flow in-to the main low path in a constant proportion over the range of values yof the pressure dierential. Although this is theoretically possible, in practice it will often be found advantageous to reduce the Vdesign requirement on the restrictors 18 and 44 for constant proportion by limiting the maximum value of P1. This is done by placing the restrictor 29 in series with parallel restrictors 18 and 44 and on the upstream side thereof.

The restrictor 29 is designed to present a narrow rigid aperture to the Huid lowing into the main ow path and is particularly designed for incompressible fluids. With an incompressible uid, and this restrictor, the higher the pressure upstream from restrictor 29, the greater the pressure drop across the restrictor. Restrictor 29 therefore acts as a limiter for pressure P1. It is of course true that as 4the pressure upstream from restrictor 29 rises, the pressure P1 will also rise. However, if the fluid tlowing in the main flow path is water, and the source of water is a municipal Water supply, the peak pressures for such supply will usually be known. sures, the restrictor 29 may be selected to ensure that up to such peak pressures P1 is within the design range for proportional metering.

It will be obvious that other means may be provided for Hunting P1 below a maximum value in spite of source pressure variations whether the iiui-d flowing in the uid s ilow path is incompressible or compressible.

The restricted fluid passage or path composed of the grooves 44 will allow ow therethrough in amounts which are linearly proportional to the pressure differential across the passage as long as the ow through the grooves 44 is laminar. This proportionality results from 'the fact that the uid ow resistance in grooves 44 is substantially all due Ato friction of the iluid on the passage walls resulting in shear in the iiuid causing ow rate substantially pro- For such peak presi' portional to pressure drop across the passage in accord with Poiseuilles law and is therefore substantially proportional to the pressure differential across the passage 'Ihe most critical dimension for laminar tiow is the diameter, and the larger the diameter the greater the laminar volume ow rate which may be obtained through the passage.

For a given restrictor 18 pressure P2 and the differential Pl-PZ is a function of P1. Thus by the use ofga relatively large diameter groove 44, flow therethrough linearly proportional to the pressure differential across the groove is possible to a relatively high range of higher pressures P1. For a relatively large groove 44 the required resistance to uid flow is obtained by increasing rthe length of the groove. The helical design of groove 44 shown, or a groove of other sinuous shape allows the desired length of path to be achieved within a compact body which may be plugl 36 and block 46 as shown, or may be other differently lshaped bodies having immediately contacting surfaces in one or both of which the sinuous grooves may be located. j

The use of a grooved surface of one member juxtaposed to a surface of another member provides a fluid passage which may be designed cheaply and accurately since fthe grooved member may be cheaply and accurately moulded out of plastic and thereafter easily cleaned if necessary. The tolerances of groove diameter which are of great -importance in determining flow rate are of somewhat less etfect with the disclosed construction because of the larger groove diameter. 'Ihe juxtaposed surfaces must tit together so accurately as to prevent any substantial leakage from the groove between the surfaces.

'Ihe valve design to be hereinafter described prevents flow of tluid from the container 22 when the ow is so low as to place the pressure differential below the linear range of design. For operation of the valve refer to FIGURES 1, 2 and 3.

A valve spindle extends downwardly into the plug aperture and the part therein is of a diameter to close the aperture 39. A groove 62 extends a short extent upwardly from the bottom of the spindle on the si-de thereof adjacent the downstream end 16 of the bore. The spindle is adapted to reciprocate vertically over a limited range of movement and lthe length 'ofdthe groove 62 is so related thereto that the upper end is exposed above the plugs 37 at the upper limit of movement of the spindle 60 but occluded at the lower extremity of movement.

The spindle projects upwardly through an aperture 64 in the body 10.

A piston cylinder is defined by a pair of opposed hanged members 66 and 68 over aperture 64 yand the spindle 60 projects into the cylinder having threaded thereon a piston 70. On the upper side of the piston 70 a compression spring 72 bearing against it biases the piston downward. Fluid inlet at pressure P1 is provided for by passages 74 and 76 in members 10 and 66 respectively. Alignmen-t of the spindle `60 during reciprocal movement is assured by a stud 78 projecting upwardly from piston 70 into a bore 80' in member 68.

A tluid tight seal between piston 70 4and. the cylinder walls is assured by membranes 82 projecting on each side thereof and clamped -between the members 66 and 68. The piston 70 and membranes 82 are preferably of plastic and may therefore be integrally made with one another.

Fluid entry through bore 64 is prevented by a similar membrane 84 clamped between member 66' and body 10 and preferably of plastic and integral rwith spindle 60. Suitable ports S6 and S8 prevent compression in the spaces above piston 70.

For the purpose of operation, let it be assumed that the upstream end of bore 12 is connected to a water line on the downstream side `of a valve which controls llow in the main ow path and that the container 22 is filled with uoride solution. Then when the valve is opened causing ow in bore 12 water ows through re- 7 Y, strictor'29 and Ythen through vrestrictor 18 andout through 'downstream end 16. The flow of water through restrictor 18 creates the pressure differential llll-P2 while restrictor '29 limits the upper value of Ps1. Simultaneously water at `pressure P1 flows through pont 30 to space 28 to apply pressure P1 to the container 22. At the same time'water flowing through ports 74 and 76 raises the piston 70 and with it spindle 60. Groove 62 is then exposed to main flow bore 12 (see FIGURE 2 and FIGURE 1). The container 22 is then (with the exception of the valve 'formed by membrane 58 which is closed) directly connected by porlts 56, grooves 44 and groove 62 to the bore 12 on the downfiow side of restrictor 1S. The pressure difierential Pl--PZ acting through bag 22 and between the inside of container 22 :through groove 44 to th-e main flow path on the downstream side rof restrictor 18 thus causes menibrane valves 5S to lift, and flow ofthe fluoride solution takes vvplace' from container 22 through grooves 44 to -bcre 12 and into the main flow.

As previously explained, the proper design of grooves 44 and restrictor 118 allows the ratio of fluoride solution to water to be kept substantially constant over the main range of values of the pressure differential. To keep the values Vof the pressure differential within the range of linear operation of grooves 44 and restrictor 18 a nonlinear restrictor 29 may be provided. The restrictor 29 `reduces the pressure P1 `below that of the line and due to the non-linearity of the restriotor the amount of reduction increases with increasing yline pressures.

The restrictor 29 will not limit higher pressure P1 .to the linear range yfor all line pressures. However the line pressures in a given municipality will usually have predetermined peak Vvalues and thus, for such municipality the characteristics of the restrictor 29 may be selected to .keep higher pressure P1 below the maximum value for linear operation even at such peak values.

The flow of fluoride solution is prevented at low values of the pressure differential by the fact that the pressure P1 is insufficient to open groove 62 to the main flow against the bias of compression spring 72. Y

v When pressure P1 drops toward yzero there'is no' pressure differential across :the restrictor 18"and no pressure on container 22. The spring 72 acts to move spindle 60 downwardly, occluding groove 62 from the main flow Y .and membrane valve 58 closes on plug S2. It will be seen that in valve piston 70 the pressure P1 is opposed, not only by the spring 72 butalso by the atmospheric pressure. However the yvariations of atmospheric pressure are so small in relation to the pressure P1 on the one hand and the spring 72 on the otherhand that they do not introduce any noticeable error in the functioning of the valve. y

It Will thus be seen that two main barriers prevent the idiffusion of fluoride solution out of ,container 22 and into main flow 12 when the main flow line valve is shut ol;

firstly, the membrane valve 58 and secondly, the occlusion of groove 62. With the main flow line valve located upstream from the inventive `device it will be obvious that the valve operated Iby spindles() for allowing or preventing flow from the container could be operated by P2 instead of P1 yas shown since for any given restrictor 18, P2 and P2K-P1 are functions of P1, and as `P1 varies so P2 will vary although in lesser amounts.

When the inventive device is located on the upstream 'side of the valve for controlling flow in the main flow path, then it will be seen that when the flow is shut off, pressures P1 and P2 will be full line pressures and the valve controlling flow from container 22 to the main flow path would notshut to prevent such flow. Thus when the main flow path valvevis located downstream from the device, the effect of pressure P1 is applied against the valve bias force and P2 is'caused to exert an effect opposite y'to P1 on the valve control, so that in a device as Vshown in the alterna-tive embodiment of FIGURE 6, when the main flow valve is shut of the effect of P2 (P2 accesos then equalling P1) plus the valve bias force will be sufllcient to move the valve against the effect of P1 to prevent flow in .the restricted passage from the container. This alternative form of the device is shown in FIGURE 6 and it will be seen that the only change from FIGURE 1 is the elimination of the passage 88 which, in FIGURE l connected the upper surface of piston 70 (through passage S6) to the atmosphere and the addition of a passage 89 which instead connects the upper surface of piston 7 0 (through passage 86) to conduit 12 in the location of downstream pressure P2. Whether the device is as shown in FIGURE 1 or in FIGURE 6 it will be seen that the valve mechanism will operate to interrupt flow from the container whenever the pressure differential across the restrictor 18 falls below a predetermined amount.

The positioning of groove 62 on the `downflow side of spindle prevents the accidental clogging of groove 62 by foreign matter or deposits from the main flow.

Finally it should be noted that between maximum and minimum values of higher pressure P1 the restricted passage embodied by groove 44 will meter iluid from the container into the main flow path at rates linearly proportional to the differential P1-P2. For predetermined line pressure peaks the restrictor 29 will keep the value of P1 below the maximum.

In some fields, not specifically discussed heretofore, a pressure drop of a second fluid ilowing in a main flow path may be used to move fluid from a container to the main flow path by causing second fluid to move from a higher pressure part of the flow path into the first fluid container itself forcing first fluid into the flow path at aV lower pressure part. Thus the bag 22 separating first fluid from second fluid may in such fields be eliminated. It will be seen that, in this case also, the sinuous groove from the container to the flow path and the flexible disc 19 may ybe used to obtain metering of some accuracy.

We claim:

l. Means for metering a first fluid into a second fluid, comprising: a conduit defining a fluid flow path; apredetermined fluid flow direction in said conduit; means for restricting flow 'of fluid lalong said conduit adapted to cause a pressure differential thereacross from a higher pressure on the upstream side of said flow Irestricting `means to a lower pressure on the downstream side of said flow restricting means, said flow restricting means being designed to allow fluid flow therepast at a volume flow rate substantially linearly proportional to said pressure differential within -a predetermined frange of said pressure differential; a compressible container for said first fluid; means lfor applying said higher pressure to the outside of said compressible container; means defining a fluid passage connecting the inside of said compressible container to said main flow line in the region of said lower pressure; said fluid passage being designed to have laminar flow of said first fluid over said predetermined range of pressure differentials.

2. Means as claimed in claim 1 wherein said fluid passage comprises a pair of bodies having respective surfaces in Contact, at least one sinuous groove in one of said surfaces; means connecting one end of said groove Yto said `container and means connecting the other end of said groove to a part of said flow path on the lower pressure side of said flow restricting means, the diameter and length of said at least one groove being such as to provide for laminar flow of said first fluid under pressure differentials between said minimum and lmaximum values.

3. Means as lclaimed in claim 1 wherein said fluid passage is lconnected at one end -to the inside of said container and at the other end to a part of said flow path on the lower pressure side of said restrictor said passage being sinuous in form.

4. Means as claimed in claim 1 in combination with means, responsive to pressure differentials lower than said predetermined range to prevent flow of iluid along said fluid passage, and responsive to pressure diercntials higher than the lower limit of said predetermined range to allow flow of fluid along said fluid passage.

5. Means as 'claimed in claim 1 in combination with means sfor supplying iiuid along said conduit at pressures less than those which will create pressure differentials above the upper limit of said range; and means, responsive to a drop in pressure differentials from values higher to values lower than the lower limit of said predetermined range, to prevent iiow of iuid along said tiuid passage, and responsive to a rise in pressure differentials from values lower to Values higher than the lower limit of said predetermined range, to allow flow of fluid along said iiuid passage.

6. Means for metering a first liquid into a second liquid, comprising: a conduit deiining the second liquid ilow path; a predetermined liquid flow direction in said conduit; means for restricting vflow of liquid along said conduit adapted to cause a pressure differential thereacross from a higher pressure on the upstream side of said ow restricting means to a lower pressure on the downstream side of said ow restricting means, said flow restricting means being designed to allow liquid flow therepast at a volume iiow rate substantially linear-ly proportional to said pressure differential within a predetermined range of pressure differentials; a compressible container for said -irst liquid; means for applying said higher pressure to the outside of said compressible container; means defining a liquid passage connecting the inside of said compressible container to said second liquid vlow path in the region of said lower pressure; said connecting conduit being designed to produce laminar ow of said first liquid over said predetermined range of pressure diierentials; wherein said flow restricting means comprises a body of exible, stretchab-le, resilient material extending across said ow path, said body being annular in form and detining an aperture, and the upstream and downstream walls of said body tapering inwardly to an edge defining said aperture, the curvature of said aperture defining edge, when viewed in the direction of iiow, being always in the same sense, said body being constructed and designed so that the pressure differential in said ow path caused by said restrictor, acts to flex the material adjacent said aperture in a downstream direction and whereby said ilexure widens said aperture.

7. Means as claimed in claim 6 wherein said liquid passage defining means `comprises a pair of bodies having mutually contacting surfaces, at least one sinuous groove in one of said surfaces, a fluid connection from said container to said groove and a uid connection from said lower pressure portion of said flow path to said groove, said groove connections being spaced along said groove.

`8. Means for metering a iirst fluid into a second fluid, comprising: means dening a flow path and iiow direction for said second fluid; means defining a iirst restrictor in said flow path, whereby with ow in said iiow path there is a pressure diierential from a higher pressure rto a lower pressure across said restrictor; a compressible container containing said ttirst iiuid; means for applying said higher pressure to the outside of said compressible container; a restricted luid connection from said container to said iiow path at a location therein on the lower pressure side of said first restrictor, whereby ow of said second fluid in said main line causes said pressure differential, whereby said higher pressure acts to compress said container and move tirst fluid through said restricted fluid connection to said ilow path; said restricted uid connection including a straight bore opening into said :tiow path in a part at said lower pressure; a spindle slidable in said bore and making a sliding tit therewith; a groove running longitudinally along said spindle `from the conduit remote end -to a location short of the conduit adjacent end thereof; means `for moving said spindle between a position where said groove is exposed to said conduit and a position where said groove is totally contained in said bore; means for controlling the movement of said spindle to cause it to assume groove-exposed position when the pressure -diierential at said iirst restrictor is above a predetermined value, and to cause said spindle to assume a position so that said groove is totally contained in said bore when said pressure differential is below a predetermined value.

9. Means 'for metering a first liquid into a second liquid, comprising: a conduit deiining the second liquid flow path; a predetermined liquid iiow direction in said conduit; means for restricting flow of liquid along said conduit adapted to cause a pressure diiiz'erential thereacross from a higher pressure on the upstream side of said ilow restricting means to a lower pressure `on the downstream side of said flow restricting means, said ow restricting means being designed to allow liquid ilow therepast at a 'volume flow rate substantially llinearly proportional to said pressure differential within a predetermined range of pressure differentials; a compressible container for said tirst liquid; means for applying said higher pressure to the outside of said compressible container; means idelining a liquid passage connecting the inside of said `compressible container to said conduit in the region of said lower pressure; said means defining a liquid passage being designed and constructed to deine a passage of a length and cross-sectional area which will produce laminar ilow in liquid passing through said passage during the existence of pressure differentials within said range.

l0. Means for metering a first fluid into a second lluid, comprising: a conduit defining a iluid iiow path; a predetermined fluid iiow direction in said conduit; means for restricting flow of fluid along said conduit adapted to cause a pressure dierential thereacross from a higher pressure on the upstream side of said flow restricting lmeans to a lower pressure on the downstream side of said -flow restricting means, said flow restricting means being designed to allow uid flow therepast at a volume iiow rate substantially linearly proportional to said pressure idifferential within a predetermined range of said pressure rdiierentials; a compressible container -for said lirst fluid; means -for applying said higher pressure to the outside of said :compressi-ble container; means delining a yiiuid passage connecting the inside of said compressible container to said main ilow line in the region of said lower pressure; said tluid passage being designed to have laminar ilow of said iirst uid over said predetermined range of pressure differentials; and having means for limiting said higher pressure to a predetermined upper limit and means for preventing iiow of iiuid along said fluid passage when said pressure difierential is below said predetermined range.

References Cited in the file of this patent UNITED STATES PATENTS 1,812,916 Zerk July 7, 1931 2,061,949 Monroe Nov. 24, 1936 2,516,096 Tornblom July 18, 19150 2,573,299 Bast Oct. 30, 1951 2,593,315 Kraft Apr. 15, 1952 2,618,510 Mills lNov. 18, 1952 2,671,691 Schnell Mar. 9, 1954 2,714,963 Lester Aug. 9, 1955 2,775,984 Dahl Jan. 1, 1957 2,865,388 Sternbergh Dec. 23, 19518 2,932,3117 Klosse Apr. 12, 1960 2,984,250 Foster May 16, 1961 3,025,876 Wol-fe Mar. 20, 196-2 3,040,774 Stenberg June 26, 1962 FOREIGN PATENTS 701,460 Great Britain Dec. 23, 1953 

1. MEANS FOR METERING A FIRST FLUID INTO A SECOND FLUID, COMPRISING: A CONDUIT DEFINING A FLUID FLOW PATH; A PREDETERMINED FLUID FLOW DIRECTION IN SAID CONDUIT; MEANS FOR RESTRICTING FLOW OF FLUID ALONG SAID CONDUIT ADAPTED TO CAUSE A PRESSURE DIFFERENTIAL THEREACROSS FROM A HIGHER PRESURE ON THE UPSTREAM SIDE OF SAID FLOW RESTRICTING MEANS TO A LOWER PRESSURE ON THE DOWNSTREAM SIDE OF SAID FLOW RESTRICTING MEANS, SAID FLOW RESTRICTING MEANS BEING DESIGNED TO ALLOW FLUID FLOW THEREPAST AT A VOLUME FLOW RATE SUBSTANTIALLY LINEARLY PROPORTIONAL TO SAID PRESSURE DIFFERENTIAL WITHIN A PREDETERMINED RANGE OF SAID PRESSURE DIFFERENTIAL; A COMPRESSIBLE CONTAINER FOR SAID FIRST FLUID; MEANS FOR APPLYING SAID HIGHER PRESURE TO THE OUT SIDE OF SAID COMPRESSIBLE CONTAINER; MEANS DEFINING A FLUID PASSAGE CONNECTING THE INSIDE OF SAID COMPRESSIBLE CONTAINER TO SAID MAIN FLOW LINE IN THE REGION OF SAID LOWER PRESSURE; SAID FLUID PASSAGE BEING DESIGNED TO HAVE LAMINAR FLOW OF SAID FIRST FLUID OVER SAID PREDETERMINED RANGE OF PRESSURE DIFFERENTIALS. 